The long-term goal of this program is to develop novel inhibitors of human sphingosine kinase (SK) that are effective as therapeutic agents. Because of its critical role in sphingolipid metabolism, we have focused on SK as an innovative molecular target for the development of new drugs for the treatment of Inflammatory Bowel Diseases (IBDs). Sphingolipids are being increasingly recognized as key mediators of apoptosis, stress responses, cell differentiation and proliferation, and are known to mediate the effects of the pro- inflammatory cytokine tumor necrosis factor-alpha (TNFalpha) that is of central importance in IBDs. We hypothesize that sphingosine-1-phosphate (S1P) produced by SK within luminal epithelial cells in response to TNFalpha is critical to the cascade of events that results in the recruitment and activation of neutrophils and mast cells that further escalate the inflammation process in IBDs. Therefore, SK is a key molecular target for the development of new therapeutic agents. In spite of accumulating evidence for a pivotal role of SK in regulating immune function, pharmacological inhibition of SK is an untested means of treating inflammatory diseases, including IBDs. This is largely due to the heretofore lack of pharmacologically useful SK inhibitors. To overcome this problem, we have recently identified novel inhibitors of human SK. These compounds are more potent than any other known SK inhibitor, and do not compete for the ATP binding site of the enzyme. We hypothesize that these SK inhibitors can be used to block the effects of inflammatory cytokines and thereby ameliorate IBD pathologies. To provide proof-of-principle evaluation of the utility of these compounds, the following Specific Aims will be addressed during Phase I of this project: 1). To determine the in vitro effects of SK inhibitors on the actions of the pro-inflammatory cytokine TNFalpha; and 2). To evaluate the therapeutic efficacies of SK inhibitors in a mouse model of ulcerative colitis. Because of our previous work that led to the identification of these compounds and the development of methods for their synthesis, as well as the demonstrated expertise of our Consultant with IBD models, we are currently in a unique position to undertake the proposed studies.